1. Field of the Invention
The present invention relates to a compressive/tensile-load-type damper made of lead (hereinafter called a "compressive/tensile-load-type lead damper"), and more particularly to a compressive/tensile-load-type lead damper that can be usefully applied to seismic isolation dampers for various kinds of equipment used in atomic power plants, thermal power plants, chemical plants, and the like.
2. Description of the Related Art
A conventional lead damper is a shearing-load-type damper that receives a shearing load upon generation of vibration and deforms accordingly to thereby absorb vibration energy. Such a lead damper has been used as a damper for damping horizontal vibrations.
FIGS. 7A-7C are front views showing examples of such a conventional lead damper. A lead damper 21 shown in FIG. 7A is formed in a quadrant shape, and its opposite ends 21a and 21b are respectively connected to structural parts 22 and 23. A lead damper 31 shown in FIG. 7B is formed in a shape of the letter L, and its opposite ends 31a and 31b are respectively connected to structural parts 32 and 33. A lead damper 41 shown in FIG. 7C has a center portion 41a formed in a quadrant shape, and its opposite ends 41b and 41c are respectively connected to structural parts 42 end 43.
All of the lead dampers 21, 31, and 41 are of a shearing-load type that deforms upon receipt of a shearing load to thereby absorb vibration energy. Each of these dampers deforms in a large amount upon receipt of a shearing load and therefore serves as an effective damper for absorbing horizontal vibrations (hereinafter referred to as a "horizontal damper").
However, when any one of the shearing-load-type lead dampers 21, 31, and 41 is used as a damper for absorbing vertical vibrations (hereinafter referred to as a "vertical damper"), it conceivably requires a large installation space. Accordingly, using the shearing-load-type lead dampers 21, 31, and 41 as a vertical damper is disadvantageous in terms of installation space and is not proper.